The invention relates to a composite electrical insulator for a medium or high voltage substation or electricity line, and in particular a composite electrical insulator comprising a support rod generally of a composite material, at least one optical fiber placed on the outer periphery of the support rod, and an outer insulating coating of a vulcanized material surrounding the support rod so as to cover the optical fiber.
Such a composite insulator is known from patent document EP-0 926 516.
In that known insulator, the insulating outer coating is compression molded around the support rod to envelop the optical fiber. In order to avoid the presence of any inclusions of air along the optical fiber placed on the support rod, an adhesive agent is used to stick the optical fiber onto the outer periphery of the support rod in such a manner as to be completely covered by the adhesive agent. The outer layer of the optical fiber can be treated to improve its adhesion with the adhesive agent, thereby very significantly increasing the cost of manufacturing the insulator.
The object of the invention is to propose another design for such a composite electrical insulator provided with optical fibers.
To this end, the invention provides a composite electrical insulator comprising a support rod generally of a composite material, at least one optical fiber placed on the outer periphery of the support rod, and an outer insulating coating of a vulcanized material surrounding the support rod so as to cover the optical fiber, wherein the optical fiber has an outer sheath of a material that is compatible with the material constituting the outer coating so that a cohesive bond forms between the outer sheath of the optical fiber and the outer coating of the insulator while the outer coating is being vulcanized. With such a structure, the outer coating of the insulator can be injected under high pressure and at high temperature around the support rod and it adheres to the outer sheath of the optical fiber and to the support rod without leaving any inclusions of air. When making an insulator of the invention, there is no need to surround the optical fiber completely in an adhesive agent, and this simplifies manufacture of the insulator. If the support rod is an epoxy resin and glass fiber composite, then the optical fiber is preferably stuck to the support rod using the epoxy resin mixture of the composite. The outer coating of the insulator is generally an elastomer, and the optical fiber is preferably selected to have an outer sheath of thermoplastic elastomer. A plurality of optical fibers, each having its own outer sheath of thermoplastic elastomer, can thus be grouped together in a ribbon by heat-sealing their outer sheaths so as to form an optical fiber ribbon which makes it easier to place the optical fibers on the support rod and to guide them away from the insulator through the metal end-fittings thereof. In addition, such a ribbon of optical fibers formed in this way by heat-sealing and placed on the support rod of the insulator is very easily undone in order to separate the ends of the optical fibers for connection to the terminals of sensors or measurement appliances.